Method and composition for making lined dipped goods from latex



R. m m 7, Wm A 2 w W m f B M. C. TEAGUE METHOD AND COMPOSITION FORMAKING LINED DIPPED GOODS FROM LATEX Filed Sept. 3, 1952 May 29, 1956liningfor the glove'adhering thereto;

United States Patent METHOD AND COMPOSITION FOR MAKING LINED DIPPEDGQODS FROM LATEX Merwyn C. Teague, Sparta, N. J., assignor to UnitedStates Rubber Company, New York, N. Y., a corporation of New JerseyApplication September 3, 1952, Serial No. 307,627

8 Claims. (Cl. 18-585) This invention relates to a new method of makingfabric-lined dipped goods from rubber latex, as well as to a newcomposition for coating a dipping form on which the latex is deposited.

In preparing fabric-lined dipped goods from latex, such as. rubbergloves, it is customary to prepare the desired fabric lining by sewingthe requisite number of parts together, just as if one were making afabric glove. This fabric lining is then slipped over the usual form,and the form is dipped into a rubber latex preparation, and removed witha coating of latex adhering to the 'fabric covered form. The latex isthen coagulated in place, and the clipping and coagulation are repeatedas fabric lining is frequently not necessary in dipped articles.

Thus, in a glove, the lining is used primarily to facilitate donning anddoffing, and to absorb perspiration so that the wearer will notexperience the clammy feeling that The fabric also serves to strengthenthe rubber. These advantages could be obtained by using a lining that isonly For example, 7

partial, with consequent saving of fabric. a lining'for a glove might becut out of two pieces,

one that will cover the palm and the inside of the fingers,

and the other to cover the back of the hand and fingers. In such aconstruction, only the sides of the fingers would remain uncovered.However, the prior art has not .aflforded any'convenientand economicalmethod of making such partially-lined dipped goods.

. The'principal' object of the present invention is therefore to providea more satisfactory method of associating a fabric lining with adip'pedrubber article.

Another object is the provision of a composition that can be applied to'adipping form'to maintain a full or partial fabric lining adhesively inplace on the form while a coating of latex is deposited thereover, butwhich will at the same time strip'free of the form without appreciableresidual tack,- after the dipped article is vulcanized;

a "The manner in which the invention accomplishes the foregoing objects,aswell as additional objects and advantages; will be'made manifest inthe following detailed descriptiom-which is intended to be read withreference to the accompanying drawings,wherein:

Fig. 1 shows a dipping form for making a rubber glove,

.the form being provided with a'pre-coating of the adhesive and'stripping composition of the invention;

Fig. -2 shows the pre-coated'form with a partial fabric Fig; 3 shows theform after clipping in rubber latex;

2,747,229 Patented May 29, 1956 ICC According to the invention, the formfor the dipped article is first coated with a special adhesivecomposition comprising a resinous styrene-isobutylene copolymer,polybutene, and a silicone fluid. The resinous styreneisobutylenecopolymer itself forms a non-tacky film, but the polybutene serves tomake the film tacky, while the silicone serves as a parting agent. Theingredients of this pre-coating composition are conveniently applied tothe form as a solution in a mutual volatile organic solvent, suchsolution being applied in any convenient manner, as by painting,spraying or dipping, followed by drying to remove the solvent. It hasbeen surprisingly found that such a pre-coating composition gives asmooth, continuous, and tacky surface on the form, and a textilematerial, which is to form the lining, especially a partial lining, ofthe clipped article, may be pressed onto the thus-coated form, to whichit will remain adhesively secured throughout the subsequent dipping,drying and vulcanizing operations. However, it is most unexpectedlyfound that after the dipped article has been vulcanized by heat on theform, the initially adhesive coating loses its tack, and the vulcanizedfabric-lined article can be readily stripped from the form with aperfectly smooth and clean finish that is essentially free fromstickiness, both on the fabric surfaces, and on the rubber surfaces thatwere in contact with the form. During the vulcanization the initiallyadhesive pre-coating transfers from the form to the rubber surface,leaving the form with a non-tacky, clean surface where it has in contactwith the rubber. The polybutene, which was responsible for the tack ofthe coating, actually goes into the rubber. The areas of the formbeneath the fabric, however, are left with a slightly tacky surface, butthe fabric nevertheless strips free without stickiness.

The fabric is preferably treated in such a manner, before it is adheredto the form, that the rubber latex will not penetrate through the fabricduring the dipping operation. Most advantageously, this is done bypreviously skim-coating the fabric with a thin layer or veneer of gumrubber on the side of the fabric that faces away from the form. This mayalso be accomplished by treating the fabric with a water-repellentmaterial, such as 2 to 3% solution of stearic acid in alcohol, which,upon drying, renders the fabric substantially impermeable to latex. Forthis purpose the fabric may initially be impregnated with such awater-repellent. The preliminary skim-coating of rubber on one side ofthe fabric is particularly desirable because it provides for goodadhesion between the fabric and the deposited latex.

The resins suitable for use in the pre-coating composition of theinvention are the copolymers of styrene and isobutylene, such as areshown in detail in U. S. Patent 2,274,749 to Smyers. These copolymersare film-forming and are normally hard, inelastic, thermoplasticmaterials, and typically contain from about 40 to 60% by weight ofcombined styrene and correspondingly from 60 to 40% of combinedisobutylene. The polybutene employed in the pre-coating composition is aknown commercially available material. This material is thick, likehoney, and the commercial grades having a melting point of from about 30to 130 C. are most suitable. Usually from about 20 to parts of thepolybutene is employed in parts of the mixture of polybutene andstyreneisobutylene resin. 7

The silicone component of the coating may be any nonresinous,non-volatile, polymeric fluid silicone having a consistency, when byitself, ranging from an oily liquid to a grease. There is usuallyemployed a commercial polymeric dimethyl silicone fluid having theformula CH3[(CH3)2SlO]zSi(CH3)3 where x is from 2 to 11. Such siliconefluids are generally mixtures of a predominating amount of one polymerof dimethylsiloxane with minor amounts of other polymers ofdimethylsiloxanes within the range of the above formula. The viscositiesof the methyl silicone oils typically range between 0.5 and 1,000centistokes at 25 C., and the specific gravities typically range from0.760 to 0.975 at 25 C. Other fluid polymeric silicones than the methylsilicones which may be used in the present invention are the ethylsilicone fluids or polymeric diethylsiloxanes, and the alkyl-arylsilicone fluids, e. g., polymeric methyl phenol siloxanes and polymericethyl phenyl siloxanes. The silicone should be soluble in and compatiblewith the polybutene and the styrene-isobutylene components of thepre-coating. For a further description of silicone fluids reference ismade to Chemistry of Silicones by E. G. Rochow, published byJohn Wiley,N. Y., 2d edition, 1951, particularly chapter 6 entitled Properties ofthe Specific Silicone Polymers and to two articles by D. C. R. Miller inCanadian Chemistry and Process Industries, vol. 33, pages 764-767,858-866 and 870.

A suitable polymeric ethyl silicone fluid for use in the presentinvention can be made in accordance with U. S. Patents 2,258,218 to E.G. Rochow; 2,377,689 to Hyde; 2,384,384 to McGregor et al.; 2,469,888 toPatnode; and 2,491,843 to Wilcock.

The silicones which are suitable for use in this invention may vary fromlight oil-like liquids to heavy jellies or greases. Examples areproducts which are sold by the Dow-Corning Corporation under thedesignation of Dow-Corning Stop Cock Grease, Dow-Corning Plug CockGrease, Dow-Corning Type 200 Fluid, Dow- Corning Type 500 Fluid,Dow-Corning Ignition Sealing Grease, and Dow-Corning Anti-Foam A.

The silicones employed usually contain from 1.98 to less than 3.0hydrocarbon radicals per silicone atom, and the hydrocarbon radicals areattached to the silicone atoms by carbon-silicon linkages. Thehydrocarbon radicals may be alkyl, aryl, aralkyl or alkaryl radicals,preference being given to the lower alkyl radicals, especially methyl.Usually from about to 50 parts of the silicone is employed in 100 partsof the mixture of polybutene and styrene-isobutylene copolymer. I preferhowever to employ from about 10 to 25 parts of the silicone per 100parts of combined styrene-isobutylene copolymer and polybutene.

In preparing the form pre-coating composition any suitable volatileorganic solvent capable of dissolving the styrene-isobutylene resin, thepolybutene and the silicone can be used. The solvent can comprise asingle material or a mixture of materials. Paratfinic hydrocarbonsolvents, such as gasoline, are suitable, as well as aromatichydrocarbon solvents, such as benzene, toluene and xylene. Othersolvents such as carbon tetrachloride are also usefill. The proportionof total solids in the coating composition can vary within wide limits,depending mainly upon the method of coating. I generally make thecoating composition quite thin, with a non-volatile material content ofless than However, compositions having a nonvolatile content of from 3to are also useful under proper conditions.

Application of a single coating of the mixture in any conventionalmanner, as by spraying or dipping, will generally give a film ofsufiicient thickness to accomplish the objectives of the invention.

The following example will serve to illustrate the invention in moredetail.

Example The following pre-coating composition was made up:

Parts by weight The polybutene employed was a commercial grade known asOronite 32. The dimethyl silicone was commercial material sold under thetrade designation DC-ZOO.

The form, such as the glove form 1 shown in the accompanying drawing, isdipped into this solution and dried for two minutes at room temperature.Evaporation of the solvent leaves a smooth, continuous, very tacky film2 on the surface of the form 1. There is then provided a fabric part 3,previously cut to the desired shape of a partial lining for the glove.The fabric is previously skimcoated on its outer surface with a thinlayer 4 of gum rubber to prevent the latex from penetrating the fabric,and to improve the adhesion of the latex to the fabric. The rubber layer4 may be of contrasting color, that is, it may be of a different colorthan the latex, or it may have any desired design or ornamentationimpressed thereon, especially if substantially transparent latex isused. A similar fabric piece is provided at each side of the form, andthe bare or inner surface of the fabric is pressed firmly against theform. Care is taken to apply firm pressure to the edges of the fabricpiece, which are the most likely portions to pop up. The fabric may beof any type suitable for lining, ranging from light sheeting to a heavyknitted fabric.

The form with the fabric panels in place is then dipped in the usualcompounded latex bath, which may be composed of any of the usualconventional dipping solutions based either on natural rubber or one ofthe synthetic rubbers, followed by a dip in an acid bath, or othercoagulant, to coagulate the latex in the form of an overlying film 5.This procedure is repeated if a thicker deposit of latex is desired,followed by a dip in a water bath to leach the deposit, if desired. Thelatex film is then cured for 40 minutes at 240 F. During the cure thepolybutene and the other ingredients of the pre-coat transfers to thedeposited rubber and becomes an intimate part thereof, with the resultthat the pre-coating composition loses its tack. It is then possible tostrip the partially lined glove 6 from the form cleanly with ease. Thereis no tackiness either on the inner rubber surface 7 or on the innersurface 8 of the fabric. The pre-coating composition transfers with therubber and the surface 9 of the form that was in contact with the rubberis nontacky, While the surface 10 of the form that was in contact withthe fabric is somewhat tacky, but not sufliciently so to result in anydifliculty in stripping the fabric cleanly. There is substantially notendency for the coating to come off with the fabric and produceobjectionable tack on the glove lining.

From the foregoing, it will be apparent that the invention provides aconvenient and economical method of making fabric-lined dipped goods,especially partiallylined articles. Time-consuming and laboriouspreparation of the fabric parts of the lining is eliminated since theydo not have to be sewed or otherwise fixed in proper relationship beforethey are associated with the form. By relying upon a special adhesivepre-coating composition to affix the fabric to the form, the method ofthe invention makes it possible, for the first time, insofar as theinventor is aware, to prepare partially lined dipped articles by a good,practical process. The use of only a partial fabric lining not onlyrepresents an economy of fabric, but also results in an article that hasmore stretch than a fully-lined article. The areas of rubber that arenot supported with fabric provide this additional stretch.

The pre-coating composition described solves the difficult problem ofholding the lining pieces securely to the form during dipping, and yetthe coating also provides for easy and clean stripping of both thefabric lining and the rubber from the form after vulcanization. Theprecoating composition therefore possesses the essentially contradictoryqualities of being a tacky adhesive when it is initially applied to theform, and an anti-adhesive stripping or parting medium aftervulcanization. The fabric stays firmly in place in precisely the desiredposition without curling or peeling during the dipping operations, andup to the point where it becomes vulcanized. After vulcanization,however, the fabric strips free of the form and retains none of the tackof the adhesive.

It is sometimes found desirable to include in the precoating compositionsome milled raw rubber to supply additional tack, particularly where thefabric must be adhered to sharply curved surfaces.

It is also possible to practice the method of the invention by employinga hard, inelastic, styrene-butadiene thermoplastic copolymer resin asthe film-forming ingredient in place of the styrene-isobutylene resin inthe composition described above. However, the styrenebutadiene resin isless preferred, and, if it is used, it is desirable to include alsoabout 50 or 100 parts, per 100 parts of resin, of milled raw rubber tosupply additional tack.

The polybutene functions as a tack-producing agent in the composition inthe initial part of the process, but, under the influence of the heat ofvulcanization, it migrates to the rubber latex film, in which it isapparently preferentially soluble, particularly under the influence ofthe heat of vulcanization, compared to its solubility in the deposit ofstyrene-isobutylene resin. Thereafter the rubber surface issubstantially non-tacky.

Although the polybutene is the preferred tackifying agent for use in theinvention, it is also possible to use polyterpene for this purpose.Polyterpene is available commercially under the trade name of Piccolyte.However, this material is less preferred.

The silicone is a highly desirable constituent of the preferredcomposition used in practicing the invention, but it is not absolutelyessential under all circumstances.

The method of the invention lends itself to the production of a varietyof interesting effects. Thus, I have made gloves of attractive design byusing a transparent latex, and a patterned fabric beneath. The fabriccan be dyed in a different or contrasting color to the latex film, or itcan have any desired design impressed upon it in any suitable manner.The fabric is advantageously colored by applying a colored rubber skimcoat thereto.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A method of making fabric-lined vulcanized rubber latex dippedarticles which comprises providing a dipping form having the desiredshape, coating the form with a composition comprising a film-formingthermoplastic resin selected from the group consisting ofstyrene-isobutylene resin and styrene-butadiene resin, and a tackifyingagent, applying the desired fabric lining against the thus-coated formin adhesive relation therewith, dipping the form in rubber latex,coagulating the latex on the form, heating the thus-deposited rubber tovulcanize the same, and thereafter stripping the resulting fabric-linedrubber article from the form.

2. A method of making fabric-lined vulcanized rubber latex dippedarticles which comprises providing a dipping form having the desiredshape, coating the form with a composition comprisingstyrene-isobutylene resin and polybutene, applying a desired fabriclining against the thus-coated form in adhesive relation therewith,dipping the form in rubber latex, coagulating the latex on the form,heating the thus-deposited rubber film to vulcanize the same, andthereafter stripping the resulting fabriclined rubber article from theform.

3. A method of making fabric-lined vulcanized rubber latex dippedarticles which comprises providing a dipping form having the desiredshape, coating the form with a composition comprising styrenedsobutyleneresin and polyterpene, applying a desired fabric lining against thethus-coated form in adhesive relation therewith, dipping the form inrubber latex, coagulating the latex on the form, heating thethus-deposited rubber film to vulcanize the same, and thereafterstripping the resulting fabriclined rubber article from the form.

4. A method of making vulcanized rubber latex dipped articles having apartial fabric lining which comprises providing a dipping form of thedesired shape, coating the form with a composition comprisingfilm-forming thermoplastic resin selected from the group consisting ofstyrene-isobutylene resin and styrene-butadiene resin, polybutene, and asilicone fluid, pressing individual pieces of fabric against theresulting tacky surface on the form to adhere the fabric to the form,dipping the form in rubber latex, coagulating the resulting film oflatex on the form, heating the thus-formed film to vulcanize the same,whereby the said coating composition on the form in contact with thesurfaces of the deposited rubber is transferred to the rubber, leaving asubstantially nontacky and non-adhesive surface on the form at saidsurfaces, and thereafter stripping the resulting partially fabric-linedrubber article from the form.

5. A method of making vulcanized rubber latex dipped articles having apartial fabric lining which comprises providing a dipping form of thedesired shape, coating the form with a composition comprising astyrene-isobutylene resin, polybutene, and a silicone fluid, pressingindividual pieces of fabric against the resulting tacky surface on theform to adhere the fabric to the form, dipping the form in rubber latex,coagulating the resulting film of latex on the form, heating thethus-formed film to vulcanize the same, whereby the said coatingcomposition on the form in contact with the surfaces of the depositedrubber is transferred to the rubber, leaving a substantially non-tackyand non-adhesive surface on the form at said surfaces, and thereafterstripping the resulting partially fabric-lined rubber article from theform.

6. A method of making vulcanized rubber latex dipped articles having apartial fabric lining which comprises providing a dipping form of thedesired shape, coating the form with a composition comprisingstyrene-butadiene resin, polybutene, and a silicone fluid, pressingindividual pieces of fabric against the resulting tacky surface on theform to adhere the fabric to the form, dipping the form in rubber latex,coagulating the resulting film of latex on the form, heating thethus-formed film to vulcanize the same, whereby the said coatingcomposition on the form in contact with the surfaces of the depositedrubber is transferred to the rubber, leaving a substantially non-tackyand non-adhesive surface on the form at said surfaces, and thereafterstripping the resulting partially fabric-lined rubber article from theform.

7. A method of making vulcanized rubber latex dipped articles having apartial fabric lining which comprises providing a dipping form of thedesired shape, coating the form with a composition comprisingstyrene-isobutylene resin, polybutene, and a silicone fluid, to providea tacky surface on the form, providing individual pieces of fabric toconstitute the said lining, the said fabric having a skim-coating ofrubber on one surface, and being exposed on the other surface, pressingthe said individual pieces of fabric against said tacky surface, withthe rubbercoated surface of the fabric facing away from the form, andthe exposed surface of the fabric in contact with said tacky surface, toadhere the lining to the form, dipping the form in rubber latex,coagulating the latex on the form, and heating the resulting rubber filmon the form to vulcanize the same.

8. A method of making vulcanized rubber transparent latex dippedarticles having a partial fabric lining of contrasting color whichcomprises providing a dipping form of the desired shape, coating theform with a temporarily adhesive composition comprisingstyrene-isobutylene resin and polybutene, to provide a tacky surface onthe form, providing individual pieces of fabric to constitute the saidlining, the said fabric having a skim-coating of rubber of contrastingcolor on one surface, and being exposed on the other surface, pressingthe said individual pieces of fabric against said'tacky surface of theform, with the rubber-coated surfacetof the fabric facing away from theform, and the exposed surface of the fabric in contact with said tackysurface, to adhere the lining to the form temporarily, dipping the formin rubber latex, coagulating the resulting film of latex on the form,heating the thusdeposited film to vulcanize the same, whereby the saidcoating composition on the form in contact with the surfaces of thedeposited rubber is transferred to the rubber, leaving a substantiallynon-tacky and non-adhesive surface on the form at said surfaces, andthereafter stripping the resulting partially fabric-lined rubber articlefrom the form.

1 UNITED STATES PATENTS Miller Dec. 21, 1915 Pope ,May 16, 1933 FoleyMay 29,1934 Diller Feb. 4,1936 Rogerson Feb. 24,1942 Winder Sept. 28,1943 Gammeter et a1. Mar. 20, 1945 Rumbold Jan. 14, 1947 FOREIGN PATENTSAustralia Mar. 21, 1946

3. A METHOD OF MAKING FABRIC-LINED VULCANIZED RUBBER LATEX DIPPEDARTICLES WHICH COMPRISES PROVIDING A DIPPING FORM HAVING THE DESIREDSHAPE, COATING THE FORM WITH A COMPOSITION COMPRISINGSTYRENE-ISOBUTYLENE RESIN AND POLYTERPENE, APPLYING A DESIRED FABRICLINING AGAINST THE THUS-COATED FORM IN ADHESIVE RELATIVE THEREWITH,DIPPING THE FORM IN RUBBER LATEX, COAGULATING THE LATEX ON THE FORM,HEATING THE THUS-DEPOSITED RUBBER FILM TO VULCANIZE THE SAME, ANDTHEREAFTER STRIPPING THE RESULTING FABRICLINED RUBBER ARTICLE FROM THEFORM.